Carbon Dioxide (CO2) that is retained and rebreathed in the bedding of prone sleeping infants is believed to be a contributing factor to an elevated risk of Sudden Infant Death Syndrome (SIDS) in these infants. In light of the fact that infants tend to roll to a prone position, and since some infants need to sleep in a prone position for medical reasons, dispersal of this CO2 to ambient levels when the infant is in the prone position is important in order to reduce the risk of SIDS.
Research has shown that a passive approach to dispersing CO2 is generally ineffective when challenged by the various positions an infant can sleep in. Therefore, active airflow has been used to dissipate the CO2. One approach to providing such active airflow is the use of a ventilated sleep surface in which air is directed upwardly through a mattress assembly upon which the infant sleeps. Examples of ventilated sleep surfaces include U.S. Pat. Nos. 5,887,304 and 5,675,852.
However, there are effective and practical limits to the airflow that are of critical importance to the health of the infant. If there is insufficient airflow, the CO2 dispersal rate is too low and CO2 retention continues to increase. On the other hand, if the airflow is too great, the baby risks being chilled without heating the airflow.
In order to deliver air where it is needed most (i.e. the microenvironment in closest proximity to the infant""s nostrils or mouth), a ventilated sleep surface system must have enough static pressure to overcome the obstructive nature of the microenvironment. Consequently, a simple measurement of airflow will not ensure adequate dispersal rates without the static pressure to back it up.
What is needed is an apparatus, system, and method for quantifying CO2 dispersal on a ventilated sleep surface by which a measured air flow rate produced by the ventilated sleep surface corresponds to a resulting amount of CO2 dispersal.
In one aspect, the invention provides a method for quantifying airflow, in the form of a measured airflow rate, through a porous surface. The method is particularly useful for ventilated sleep surfaces used to prevent SIDS. Provided that one knows the correlation between air flow rate and CO2 washout times, the resulting measured airflow rate provides an indication of whether a ventilated sleep surface is providing sufficient airflow to effectively dissipate the CO2.
In another aspect, the invention provides a ventilated sleep surface system that has air flow that is sufficient to produce a minimum flow rate measured by a flow meter. Based upon the correlation between airflow rates and washout times, one can determine a minimum airflow rate that results in sufficient CO2 dispersal. Thus, by operating the ventilated sleep surface system with an air flow that produces the measured minimum flow rate, a person knows that adequate CO2 dispersal is being achieved, thereby reducing the risk of SIDS.
In yet another aspect, the invention provides a flow meter allowing an accurate measurement of the airflow rate produced by a porous surface, such as used on a ventilated sleep surface.
In one embodiment in accordance with the invention, a method of measuring airflow through a porous surface includes accumulating a portion of the air that flows through the porous surface; concentrating the accumulated portion of air; and measuring the airflow rate of the concentrated portion of air.
In yet another embodiment of the invention, a ventilated sleep surface system includes a porous cover, with the porous cover including a plurality of holes therein, and a fan for producing air flow through the plurality of holes. The flow of air through the holes is sufficient to produce a flow rate, as measured by a meter having an accumulator and a concentrator, that is effective to dissipate CO2.
In still another embodiment of the invention, an airflow meter comprises an accumulator including an open bottom, a plurality of side walls and a top wall. The plurality of side walls and the top wall define a hollow interior. An elongated concentrator is connected to the top wall and projects upwardly therefrom. The concentrator includes a flow passage extending longitudinally therethrough, with the flow passage being in flow communication with the hollow interior. Further, an access nipple is connected to the concentrator, with the access nipple including a central passage in flow communication with the flow passage.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying description, in which there is described a preferred embodiment of the invention.